KARACHI, Pakistan— A blast apparently caused by explosives stored in a house in the southern Pakistani city of Karachi killed at least seven people Friday, some of whom may have been militants, police said.

The explosion occurred in Baldia, a mostly ethnic Pashtun neighborhood that is a suspected Taliban hide-out, police Chief Wasim Ahmad told The Associated Press. Its exact cause was unclear. TV footage showed police seizing guns, suicide vests and grenades from the site.

Federal Interior Minister Rehman Malik said some people from the Swat Valley, a region where the army has waged an offensive against the Taliban, were believed to have been staying at the house along with some guests, but he stressed the investigation was ongoing.

Local resident Noor Mohammed said he rushed to the scene just after the explosion and saw some of the dead men were wearing camouflage jackets. He said the men moved into the house about three months ago.

On Dec. 28, a bomb attack on a minority Shiite Muslim religious procession in the city killed 43 people and wounded dozens. Riots broke out after the attack, with people setting fire to the country's largest wholesale market. The blaze burned for more than two days and destroyed thousands of shops.

Karachi, Pakistan's largest city and commercial hub, has largely been spared the Taliban-linked violence that has struck much of the rest of the country, something analysts say may be because of the group's tendency to use it as a place to rest and raise money.

But the city has a long history of violence, much of it driven by ethnic hatred between Pashtuns and Urdu-speaking descendants of refugees from British-colonial India.

Malik said authorities plan to crack down on "illegal immigrants" in Karachi — a possible reference to Afghans, many of them Pashtun, who reside in vast settlements on the city's outskirts. He said such illegal immigrants should leave the city in the next 15 days.

Also Friday, a group of U.S. lawmakers, including Sens. John McCain and Joseph Lieberman, met with top officials in Pakistan. During a news briefing, McCain and Lieberman stressed their support for U.S. missile strikes on Pakistani territory.

The strikes are controversial in Pakistan, where the government argues they are a violation of its sovereignty and kill too many innocent civilians. However, the U.S. says the attacks are a critical tool in killing top militant leaders. (AP)