An autopsy revealed that the American security workers that died on the Maersk Alabama last week suffered from respiratory failure and suspected heart attacks, CNN reported.
According to a police statement, further tests will be performed to see if Jeffrey Reynolds and Mark Kennedy took any drugs that may have triggered the health problems.
Officers in Seychelles announced last week they discovered drug paraphernalia with the men, though their claims have not been confirmed by U.S. officials.
"The police preliminary investigation report includes suspicion of drug use, as indicated by the presence of a syringe and traces of heroin which were found in the cabin," the statement said.
Reynolds and Kennedy, both 44, worked for the Virginia-based Trident Group -- a maritime security services firm. Trident President Tom Rothrauff said both men were former Navy SEALs.
"It's bizarre. Of course, it's a shock. They're all great guys," Trident President Tom Rothrauff said. "I'm absolutely clueless as to what happened."
The 2013 film "Captain Phillips" was inspired by the 2009 hijacking of the Maersk Alabama near East Africa.
