A prosecutor in Mexico said Monday that a gas leak in a water heater is suspected in the death of an Iowa couple and their two children last week.

The head prosecutor of the Caribbean coast state of Quintana Roo told local media Monday that an inspection over the weekend revealed that the water heater at the rented condominium in the resort town of Tulum was leaking gas.

“Unfortunately, they found the area where the water heater was letting gas escape, perhaps because of a lack of maintenance, perhaps because it was in use, perhaps because of the age of the equipment,” prosecutor Miguel Angel Pech told the Radio Formula station.

“In fact, a high concentration of this toxic (gas) was found in the room,” Pech said.

He described a grisly scene: The family was found on Friday and had been dead for 36 to 48 hours by that time, according to autopsy results.

“Some were lying in their bedrooms, and the children were playing, one in one part of the room and the other in another part of the same room,” Pech said.

The autopsies indicate the family died from inhaling toxic gas, but the source or nature of the gas hadn’t been determined.

Pech said forensic samples had been sent to labs in Mexico City on Monday, and officials hope to identify the gas within eight to 10 days.

Iowa officials identified the family as Kevin Sharp, 41; his wife, Amy Sharp, 38, and their children Sterling, 12, and Adrianna, 7. They were from Creston, Iowa.

The family was reported missing by relatives about a week after they left for vacation. Creston police contacted the U.S. Department of State, and the bodies were found during a welfare check at their condo in Tulum, on the Yucatan Peninsula.

The Creston News Advertiser newspaper reported that the family flew to Cancun on March 14. According to her sister, Amy Sharp texted their mother the next day to say they had reached Tulum, but relatives didn’t hear anything else.

The sister, Renee Hoyt, said the Sharps were scheduled to depart from the Cancun airport last Wednesday and fly to St. Louis on a non-stop flight. The family had planned to then drive about 200 miles (322 kilometers) to Danville, Illinois to watch a basketball game Thursday, Hoyt said.

When the family didn’t arrive in St. Louis, family members contacted authorities, she said.

Contacted Friday, the developer of the condo complex where the deaths occurred declined to comment.

It wouldn’t be the first time that faulty gas connections killed tourists in the area.

In 2010, the explosion of an improperly installed gas line at a hotel in the nearby town of Playa del Carmen killed five Canadian tourists and two Mexicans.

In that case, prosecutors said the heating-gas line, apparently meant to fuel a pool heating unit, was not properly installed or maintained. They claimed a leak from the line may have been set off by a spark from an electric switch or plug.

A judge later dismissed criminal charges against five contractors and employees at the hotel.

(AP)