HOUSTON (AP) _ One man was killed and three more were injured Monday when sewer gases overcame them, trapping them about 10 feet underground in a manhole.

Fire officials suspect a hydrogen sulfide and carbon monoxide overcame three workers. A fourth man then went into the manhole, noticed the ailing workers and the stench and escaped to call rescuers.

``When they collapsed, they were basically on top of each other,'' Houston Fire Department Capt. Keith Bobbit said.

The first two men pulled from the hole were listed in serious and critical condition, Hermann Hospital spokeswoman Gretchen Casey said. Rescue workers were unable to resuscitate the last man hoisted out Monday afternoon.

The man who discovered the others was listed in good condition.