Firefighters who spent half an hour fighting a blaze in which 2,000 pounds of marijuana went up in smoke breathed so much of it that they would have failed a drug test, a fire chief said.

It took more than 35 firefighters, 1,000 gallons of water and five gallons of chemical suppressant to extinguish the warehouse blaze on Wednesday, Fire Chief Shawn Snider said.

U.S. Immigration and Customs Enforcement agents were investigating the origin of the drugs. The Hidalgo County fire marshal was investigating whether arson was the cause.

Snider said Thursday the firefighters were exposed to so much marijuana smoke that they would not be able to pass a drug test, despite wearing air packs to prevent them from inhaling toxic or hazardous fumes.