By Chris Williams and Jason Hanna

MUNICH (CNN) — A police operation is underway after gunfire erupted at a shopping center in Munich Friday. CNN affiliate NTV reports several are dead and others are wounded. Authorities shut down public transportation and warned people to stay home or seek protection.

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Here’s what we know so far:

At least one shooter is still on the loose after a shooting inside a McDonald’s across from the Olympia shopping mall, police spokeswoman Claudia Kantzel said. “There could be several dead and one or even several shooters are on the loose,” Kantzel said. The shooting at the McDonald’s happened around 5:50 p.m. (11:50 a.m. ET), she said. It’s unclear whether shootings have occurred at other locations, and whether the gunfire has stopped.

Gunfire also broke out inside the mall, witnesses said.

On Facebook, police said gunfire was reported in several locations, and that witnesses report seeing three different people with firearms.

“At the moment, we have not been able to arrest any perpetrators. The manhunt is underway at high speed,” police said. “Because of the unclear situation we ask all people in the city area to stay at home or to look for protection in any nearby building. The operation of public transportation service has been stopped.”

Lynn Stein, who said she works at the Jack Wolfskin store in the mall, told CNN that the shooter was inside the mall. “I heard several shots,” Stein said. “(I) was just going to buy something while my co-worker was still in the shop.

“People started running. I went outside as well; more people (were) running outside. I think I heard more shots. Then it sounded like he went to the parking house next to the mall — several shots there.”

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Stein said she then went back into the mall.

“I saw … somebody lying on the floor, presumably dead, I don’t know. Or badly hurt. And there’s a woman over them, crying.”

Eventually, she said, police “told everyone to clear off the area and go to the other side of the street.”

“And we just stayed there for a while until police told us to go further back and further back,” she said.

A string of recent terror attacks have put Europe on high alert.

A truck plowed into a crowd of Bastille Day revelers in Nice, France, last week, killing more than 80 people.

This week, a teenager who said he was inspired by ISIS stabbed passengers on a German train before police shot him dead.

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