President Trump said Wednesday night that the EPA will be issuing a “notice” to San Francisco over environmental issues caused by the city’s homeless population.

“We can’t have our cities going to hell,” Trump said. “These are great cities. And we can’t lose our great cities like this.”

Trump made the remarks to reporters aboard Air Force One while flying back to Washington D.C. after a visit to the US-Mexico border in California.

The president said drugs were causing a blight on the environment, particularly in San Francisco where “tremendous pollution” and “needles” are being funneled into the ocean from the storm sewers.

“[The] EPA is going to be putting out a notice. They’re in serious violation,” Trump said. “And this is environmental… and they have to clean it up.”

Trump said more information about the “notice” would be available in less than a week.

“It’s a terrible situation – that’s in Los Angeles and in San Francisco,” Trump said. “And we’re going to be giving San Francisco, they’re in total violation, we’re going to be giving them a notice very soon.”

Homelessness in the state has shot up over the past two years, with Los Angeles registering a 12 percent increase and San Francisco’s homeless population increasing by 17 percent, the Wall Street Journal reported.