U. S. and British experts joined their Indian counterparts in investigating last week's terror carnage in Mumbai, where life is slowly returning to normal.

The foreign investigators arrived in India in the midst of rising frustration among Indians, who say they were let down by the government's failure to combat escalating terrorism in the country.

The U. S. team is comprised of seven members from the Federal Bureau of Investigation, the Press Trust of India reported. A team from Britain's Scotland Yard is also in India.

The death toll in Mumbai has been put at 173, including 15 foreign nationals, among them six Americans.

While the FBI involvement relates to the American casualties, the British experts also want to know whether the terrorists had any links to their country. Some earlier reports had suggested some of the terrorists were British-born Pakistanis.

Separately, a CNN report said India had been warned by the United States twice in the past month about a possible maritime terrorist attack.

The gunmen, who went on a massacre spree last Wednesday before their siege ended three days later, are widely believed to have entered Mumbai using rubber boats after traveling in a trawler.

India has claimed the attacks were planned in Pakistan by the Lashkar-e-Taibas, linked to al-Qaida.

Pakistan says the government had yet to get any evidence about the involvement of militants in its territory.

On Monday, Pakistan's ambassador was summoned to the Indian Foreign Ministry amid signs the attacks may have dealt a serious blow to the fragile peace between the two nuclear nations.

Malik was handed a protest note over Islamabad's alleged failure to curb terrorism on its territory, PTI reported.