What led to the death of a Texas contractor two months ago at the CF Industries fertilizer complex in Donaldsonville remains under wraps while a federal workplace safety probe continues, authorities said.

The Ascension Parish Coroner’s Office has refused to say what killed Teodoro Silva Jr., 30, of Mercedes, Texas, and on Thursday pointed to an ongoing U.S. Occupational Safety and Health Administration investigation as the reason for the silence.

State law allows coroners to withhold disclosure of an autopsy report when it can be reasonably expected to be tied to a pending criminal investigation, but Ascension Parish sheriff’s deputies have said Silva’s death is not a homicide.

Under federal law, though, the most serious OSHA probes also can be referred for criminal prosecution.

Silva, who was working inside a completed tower more than 100 feet tall, was found unresponsive shortly before 1:15 p.m. Dec. 4 at the bottom of the vessel, CF officials have said.

A mechanic with Sulzer Chemtech’s field service unit, Silva was taken to Prevost Memorial Hospital in Donaldsonville, where he was pronounced dead the same day. CF Industries has been undergoing a $2.1 billion expansion.

In response to a public records request from The Advocate, Coroner Dr. John Fraiche refused Jan. 25 to disclose the cause of death, saying the “case is still under investigation.”

He wrote in the email response that once the probe — he did not identify the investigating agency — was finished, “we will be happy to provide you with the information requested.”

Sheriff’s Capt. Kevin Hanna responded on Jan. 26 that sheriff’s deputies were almost wrapping up their probe, and no indications of foul play or an otherwise suspicious death were found.

“Based on our investigation, no, it is not a homicide. We are not investigating a homicide at CF Industries, so I don’t know what that means (that) it’s still under investigation,” Hanna said then.

The Coroner’s Office was asked about Hanna’s comments Jan. 26 and, on Thursday, more than two weeks later, clarified that the pending probe was OSHA’s.

“I have received confirmation from OSHA that this case is still under investigation,” Fraiche wrote.

Officials with Sulzer announced in the days after Silva’s death that they were cooperating with OSHA as part of their own company probe.

Mike Lochbaum, Sulzer safety manager, said Friday he could not comment on the incident due to the investigation.

Juan Rodriguez, OSHA spokesman, confirmed the pending probe but, when asked about cause of death, added it is too soon to make any determinations. Sulzer is a contractor on CF’s expansion.

Already the largest in North America, the CF nitrogen fertilizer manufacturing plant in west Ascension Parish will see its capacity boosted by another 40 percent once the expansion is finished later this year.

Sulzer Chemtech is part of a Swiss company that builds pumps and other chemical mixing equipment.

Follow David J. Mitchell on Twitter, @NewsieDave.