By Hamid Shalizi

KABUL (Reuters) - Hundreds of insurgents who escaped from a jail in Afghanistan's volatile south through a tunnel dug by the Taliban must have received inside help from prison guards or officials, the Afghan government said on Tuesday.

Afghan authorities and foreign troops have launched a manhunt after Monday's embarrassing breakout, which President Hamid Karzai's office called a "disaster" ahead of the summer fighting months and as NATO and the United States begin preparing for a gradual withdrawal.

Tooryalai Wesa, the governor of southern Kandahar province, also said on Tuesday 65 of the 488 prisoners who escaped had been recaptured. The Taliban said as many 541 had escaped through the tunnel and were later driven away.

Justice Minister Habibullah Ghaleb, in a letter to Karzai, laid much of the blame for the mass breakout from Kandahar's Sarposa jail on failings by Afghan security forces and foreign troops.

The house where the entrance to the 320-meter long tunnel began lay within sight of the high-security prison and was searched not long before the breakout, Ghaleb said. The Taliban have said the tunnel took five months to build.

"The house where the tunnel was found was searched by security forces two-and-a-half months ago," he said, according to a statement released by Karzai's office.

"Earth or soil dug out of the tunnel must have been moved and should not have been missed by the eyes of the security forces," Ghaleb said.

General Ghulam Dastgir, the governor of the jail, said many of the prisoners still on the run had likely fled to safe havens in neighboring Pakistan.

Security has been tightened along the often-porous 2,400 km (1,490 miles) border and Dastgir said biometric data held on all prisoners at the jail would help in the capture of others.

Still, many of the escapees are experienced fighters and their breakout is a serious blow so close to the start of the fighting months. It also came after a concerted NATO and Afghan campaign to capture militants over the past year.

Images of the tunnel released so far show a hole about one meter wide, descending into compacted dirt with footholds in the tunnel sides. Steel poles were used to place car jacks under the concrete cell floor, cracking it open.

Dastgir said the cell block in which the earth tunnel entered was more like a compound, with prisoners free to move between rooms and no lock on individual doors.

But Ghaleb said only the inmates of each cell room should have had access under normal prison procedure, while vehicles used to move the prisoners should have been spotted.

"The mass escape of the prisoners from one cell indicates inside help and facilitation from the prison," he said.

In a swipe at American security officials helping oversee the jail after taking over from Canadians, Ghaleb said U.S. authorities had been busy inside the jail for months building residential rooms and judicial offices, as the tunnel took shape underneath their noses.

Afghanistan's government has launched a full investigation into the breakout, the second in three years at the jail, which Karzai's chief spokesman said had exposed serious holes in the country's security preparedness.

In 2008, around 1,000 prisoners including Taliban fighters escaped after a truck bomb blew open the jail gates. That mass escape quickly led to a surge in fighting.

(Writing by Rob Taylor; Editing by Paul Tait)