WASHINGTON — Two or three Americans and one Briton were among those who attacked a Nairobi shopping mall, Kenya’s foreign minister said Monday.

More than 60 people have been killed in the assault on the upscale mall, which has lasted for three days.

The foreign minister, Amina Mohamed, said in an interview with PBS’ “NewsHour” program that the Americans were 18 to 19 years old, of Somali or Arab origin and lived “in Minnesota and one other place” in the U.S. The attacker from Britain was a woman who has “done this many times before,” Mohamed said.

Authorities in Kenya were trying to wrap up their bloody standoff with al-Shabab, a group allied with al-Qaida.

Islamic militants who staged a deadly attack on a Kenya mall said today hostages are still alive and fighters are “still holding their ground,” as Nairobi’s city morgue braced for the arrival of a large number of bodies of people killed, an official said.

The Kenyan Red Cross has confirmed at least 62 people have been killed, but spokesman Abbas Gullet said it was still not known how many more may be dead inside the building.

“It is certainly known that there are more casualties,” he said.

A government official told The Associated Press the morgue was preparing for up to 60 bodies, though the official didn’t know an exact count. The government official insisted on anonymity so he would not face retribution from government officials.

U.S. officials said they were looking into whether any Americans were involved. State Department spokeswoman Jen Psaki said Monday the department had “no definitive evidence of the nationalities or the identities” of the attackers.

White House spokesman Ben Rhodes said U.S. officials have seen “reports coming out of al-Shabab that indicate information along those lines,” referring to possible involvement of Americans in the attack.