DENVER (AP) — Four Colorado veterans are the latest to file "burn pit" lawsuits against military contractors accused of exposing soldiers to toxic fumes and ash.

The veterans are suing Houston-based Halliburton Co. and KBR Inc., which have been accused in several lawsuits around the country of operating dangerous war-zone burn pits.

The Colorado lawsuit, filed in Denver Friday, cites four veterans who suffer from breathing problems after being deployed near burn pits in Iraq. One of the veterans says he also has kidney disease and migraines as a result of being exposed to dangerous toxins between 2003 and 2006.

The suit seeks unspecified damages. Similar suits are pending in at least 11 other states. The contractors have denied wrongdoing.