New Orleans — After Monday’s bombing at the Boston Marathon, law enforcement officials all over the country urged residents to be extra vigilant for suspicious packages and people, a request that was echoed in New Orleans by more than a dozen officials at a Tuesday news conference.

They called it the first line of defense against terrorism.

But increased public vigilance can have unintended consequences. In Mandeville, police blocked off streets for hours after an abandoned briefcase was discovered in a garbage can at a post office. In New Orleans, police investigated three suspicious packages in two days with officers cordoning off the Mercedes-Benz Superdome for hours on Wednesday night because of an abandoned briefcase, and then examining a suitcase and lunchbox on Thursday.

Kenner Police Chief Steve Caraway said his officers had to examine an ice chest at one of the city’s hotels.

None of those incidents turned out to involve threats or dangerous materials, but law enforcement officials had to mobilize their resources just the same.

In a time of shrinking police budgets and reduced staffing, investigating those complaints can put a strain on departments large and small because no agency wants to ignore a warning that leads to a disaster.

A more disturbing incident occurred on Thursday afternoon, when the New Orleans Police Department received a 9-1-1 call from an unidentified man who said, “There is a bomb in the Marriott Hotel and it’s about to blow.”

All Mariott hotels in the downtown area were immediately notified and officers were dispersed to inspect every floor of every hotel in search of anything that appeared to be suspicious, according to a news release issued jointly by the NOPD and FBI.

After an employee at the Mariott at 555 Canal Street alerted management that a backpack had been left unattended for some time in one of the bar areas, the release said, guests and staff were evacuated from the building until a bomb-sniffing dog could be brought in to determine there were no explosives in the backpack.

FBI New Orleans Special Agent in Charge Michael Anderson stressed in a statement that “bomb threats and hoaxes are acts of terror that are and will be investigated with the full weight of federal, state and local resources.”

Investigating such threats can place a burden on law enforcement at all levels.

“When we handle something like that it does tax our resources,” said Lt. Gerald Sticker, a spokesman with the Mandeville Police Department. “It’s an adjustment, but that’s kind of the cost of doing business.”

For smaller agencies, reports of potential bombs or other threats can cause serious scrambling as departments try to investigate the threat while also maintaining their normal patrols. Sticker said Mandeville has about 38 sworn officers, and relies on the St. Tammany Parish Sheriff’s Office to investigate most potential bombs. In Jefferson Parish, officials in Westwego and Gretna have a similar understanding with the Jefferson Parish Sheriff’s Office.

But smaller agencies are the ones that establish the initial perimeters or handle evacuations. Sticker said that when a post office employee called about the briefcase Wednesday, Mandeville Police had to pull in officers from other divisions and even other agencies to assist its patrol officers.

Sticker said a postal worker thought the bag was suspicious because it seemed new, and too neatly placed in the garbage, although a man later called police and said he’d just thrown it away.

Gretna Deputy Chief Anthony Christiana said his agency, which has more than 100 officers, maintains its own special operations team but doesn’t actual try to detonate or move potential explosive devices.

Gretna has not had any reports of suspicious items, and Christiana said the department’s command staff would have to determine the best response if one came in.

“It’s all about your source of information and the situation,” said Christiana, who is not surprised by the false reports in other areas. “When things of this nature happen, quite naturally your awareness level goes up.”

NOPD Officer Frank Robertson said that in the three recent New Orleans incidents involving reports of suspicious packages, police were called out by residents who were concerned in the wake of the Boston bombing.

The NOPD’s investigations included bomb-sniffing dogs, robots, X-ray machines and dozens of officers. Robertson noted that when police blocked off access to the Superdome, they had to surround the entire building, which required drawing in officers from other districts. While these incidents can create logistical nightmares for police, they are part of the process after a high-profile attack, he said.

“That’s just the job,” Robertson said.

Col. John Fortunato, a JPSO spokesman, said the agency had two reports of suspicious packages since Monday.

In one case, a man had left his bag unattended at a bus stop for only a few minutes before an alert citizen called it in. Fortunato said in both cases the responding deputies were able to assess the situation and determine that a more serious response wasn’t needed.

When tactical teams are called out, it’s always unclear how long they will be on the scene, he noted. Often deputies leave their regular assignments to come to scenes, and depending on their schedules it can result in overtime, Fortunato said.

“It could be a minute, or it could be a day,” he noted.

However, given the potential consequences, investigators don’t mind chasing down all of the public’s calls because they understand that ignoring them could have dire consequences, Fortunato said.

“It has to be done,” he said.