[img]http://d.yimg.com/a/p/ap/20100408/capt.dde1bb52770a48d2bb44ee71ab6cf441-dde1bb52770a48d2bb44ee71ab6cf441-0.jpg?x=130&y=86&q=85&sig=P3FGtWJJF00vkO51lo4L2A--[/img]AP - A federal safety official said more air testing would be needed before rescue teams could head back into a West Virginia coal mine Thursday night to look for four miners missing since an explosion killed 25 workers.