BENSALEM, Pa. (AP) - An official says the rescue effort has ended for a worker trapped underground by a gas explosion in Pennsylvania.

Fire Battalion Chief Rob Sponheimer on Wednesday says it has become a recovery effort because of high gas levels where the man was trapped following the blast at the Liberty Gas station in Bensalem Township around 5 p.m. Tuesday.

The explosion left another worker in critical condition with burns.

Public Safety Director Fred Harran says the worker who was trapped was under heavy concrete that was blown apart in the blast. Rescue crews were moving the overturned concrete with cranes and were trying to siphon fumes off.

The cause of the explosion is under investigation.

Firefighters from Philadelphia and other surrounding areas responded to the scene.

Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.