About 150 Americans including sailors are suing Tokyo Electric for $5 billion (¥545 billion) in compensation over radiation exposure from the 2011 triple reactor meltdowns in Fukushima Prefecture, the utility said Thursday.

The lawsuit was filed at a federal court in California by U.S.-based residents including personnel involved in Operation Tomodachi, the U.S. military relief effort launched for the massive earthquake and tsunami on March 11, 2011, that tipped the Fukushima No. 1 nuclear plant into meltdown.

The plaintiffs want Tokyo Electric Power Company Holdings Inc. (Tepco) and a U.S. company to set up a compensation fund to cover medical treatment and other related costs, the utility said without naming the company involved.