LOS ANGELES (AP) — Demonstrators wearing hazmat suits have protested at a Los Angeles gas field to mark the second anniversary of a gigantic methane leak that forced thousands from their homes.

About 100 protesters gathered for hours Monday at the Aliso Canyon underground storage field, claiming it's a health and safety threat. They held tombstone-shaped signs and demanded Gov. Jerry Brown close the field, which recently resumed operations.

At one point, a big-rig nearly hit a crowd at the entrance.

The Los Angeles Daily News reports that about 20 protesters were arrested when they failed to disperse after police declared an illegal assembly.

A leak in a well at the field was discovered on Oct. 23, 2014. It lasted nearly four months and caused the largest single release of methane in U.S. history.