Federal mine inspectors are being told to increase their enforcement of regulations governing the ventilation of underground coal mines.

Mine Safety and Health Administrator director Joe Main said Monday the effort stems from testimony presented in May during a congressional hearing on the Upper Big Branch mine explosion. The April 5 blast in West Virginia killed 29 coal miners.

Testimony during the House Education and Labor Committee hearing raised questions about how the Massey Energy mine was ventilated.

Main says in addition to notifying inspectors, the agency is reminding companies to pay attention to laws and regulations governing how mines are to be ventilated.