BRIGHTON, Colo. -- During raids on 25 marijuana grow operations across Colorado this week, authorities said they seized lots of guns, pot, cash and, surprisingly, 15 million in Iraqi Dinar currency.

At a Friday news briefing in Brighton, law enforcement officials displayed some of the loot seized in Operation Sweet Leaf, the Wednesday raids that netted 13 arrests.

They also warned of the dangers that grow houses pose to the people, including children, who live inside them.

The haul included:

• 40 guns
• 2,749 marijuana plants
• 147 pound of dried pot
• Over $278,500 in cash
• 15 million in Iraqi Dinar currency

Asked to explain the pile of Iraqi currency, officials said the ongoing investigation prevented them from discussing it.

Don Quick, district attorney for Adams and Broomfield counties, said the vast majority of the marijuana was being shipped out of Colorado. Destinations included California, Iowa, Kansas, Nebraska, New Jersey, Pennsylvania and Texas.

Authorities said those arrested were not involved in growing medical marijuana.

Quick said the mult-iagency investigation began 10 months ago when authorities in another state made a major marijuana seizure and learned the pot had been grown in Colorado.

Colorado investigators found that traffickers were using the U.S. mail to ship both the marijuana and huge amounts of cash.

One parcel contained $10,000, said Pam Durkee of the United States Postal Inspection Service.

An indictment said the ring was headed by 22-year-old Jordan Buehrer of Thornton.

The raids hit two dozen homes from quiet metro Denver suburbs to Breckenridge.

Authorities said a total of seven children were removed from homes and placed in the care of social services.

Dr. John Martyny, an expert in environmental diseases at National Jewish Hospital, said a year-long study of 24 indoor grow operations found health hazards for people living in the houses and to narcotics agents raiding them.

The indoor grows used a lot of heat lamps and water, which create "incredibly elevated levels of mold that pose a definite health hazard to law enforcement officers coming in and also to people living there, especially the children," Martyny said.

"These high (mold) levels can cause a lot of pulmonary problems, especially if the exposure lasts for a long period of long time," he said. "In a young child, the impact could last for the rest of their life."

Martyny said pot growers also use dangerously high levels of carbon dioxide to spur plant growth. They sometimes tamper with furnace and water heater vents to trap the gas in the homes.

Other contaminants include massive amounts of fertilizer and pesticides that are not intended for indoor use, he said.