SALEM, Ore. - Federal officials are investigating a marijuana processing facility in Oregon after an explosion there injured a man who was previously convicted in a money laundering operation linked to pot trafficking.

The probe is a fairly rare instance in which U.S. officials are investigating a marijuana case in a state where pot is legal. Federal enforcement of U.S. laws that ban possession and distribution of marijuana is restricted by the U.S. Justice Department, but is permitted when marijuana is being distributed to other states and in a few other situations.

Police in Cottage Grove, a Willamette Valley town of 10,000, called on the U.S. Drug Enforcement Administration for help after fire officials found hundreds of marijuana plants growing inside the building where the explosion occurred Nov. 16. The explosion burned a man who was on parole after serving a 90-day sentence in the money laundering operation, The Register-Guard, a newspaper in the nearby city of Eugene, reported.

"We have a large amount of marijuana grows," Capt. Doug Skaggs of the Cottage Grove Police Department said in a telephone interview. "We're not different than everyone else (in Oregon)."

Skaggs said that because of manpower issues, the police department often liaises with the DEA.

A report by The Associated Press in August showed that large amounts of marijuana are being smuggled out of Oregon, although what percent of the tons grown in the state is trafficked is hotly debated. Local law enforcement in Oregon is often too strapped for personnel and money, and is busy with other investigations and mindful of restrictions against searches without cause, to figure out which grows are registered and legal and which are illegal.

When DEA agent Sean Cummings got a warrant the day after the explosion and searched the building, he found 728 growing pot plants, 1,200 pounds of marijuana, and marijuana extracts, according to federal court documents. That address was not authorized by

Oregon authorities to grow or process marijuana, the court documents say.

Eric Scully, who was burned on the face and hands in the explosion which was apparently caused by combustible materials used to make marijuana oil, had been on parole after accepting a plea agreement in federal court last year. Investigators said he had shipped marijuana grown in Oregon via the mail to states where it remains illegal. Cottage Grove is also next to Interstate 5, a major drug-trafficking route.

Scully and two co-defendants in that money-laundering case earned more than $1 million, authorities alleged. A coffee kiosk that Scully owned was used to launder the proceeds.