HEMPSTEAD, Texas—A man charged with murder was on the loose Saturday after he broke out of jail by climbing through an air conditioner vent, authorities said.

The vent was less than a foot wide, and authorities said Darryl Layne Norris had been losing weight since being taken to Waller County Jail in April.

“We just found out he’s been slimming down a lot recently,” Waller County Sheriff Randy Smith said.

The escape happened a few hours after midnight Saturday, Smith said. The jail noticed Norris, who was described as about 6-feet tall and 160 pounds, was missing after performing a routine head count.

Norris, 26, and another man are charged with murder in connection to an April 17 convenience store robbery. Smith did not know if Norris was armed but considered him to be dangerous because of the charge.

The Texas Rangers were assisting in the investigation, Smith said.

Hempstead is about 50 miles northwest of Houston.