Tutu told reporters in Gaza the blockade had to be lifted because "it is a gross violation of human rights".
On Wednesday, Tutu said he had asked Ismail Haniya, prime minister of Gaza's Hamas government: "Can you stop the firing of rockets into Israel?"
Haniya was dismissed by Mahmud Abbas, the Palestinian president, last June when Hamas took control of Gaza from forces loyal to Abbas.
"The incident we are meant to investigate was a violation of human rights in the fact that civilians were targeted," Tutu said.
"We have said to the prime minister [Haniya] that equally, what happens with rockets fired at Sderot is a violation."
Tutu, who was a prominent anti-apartheid activist when South Africa was still under white minority rule, said it was crucial that the two sides negotiate.
|Eight children were among the dead in the|
November 2006 attack [File: GALLO/GETTY]
"That was our experience in South Africa. Peace came when former enemies sat down to talk," he said.
The team visited Beit Hanoun on Wednesday, where the 2006 killings occurred, to interview witnesses and survivors of the attack.
They will prepare a report to present to the UN Human Rights Council in Geneva.
The Israeli attack on Beit Hanoun was widely condemned by the international community for killing 19 civilians, including five women and eight children in their homes.
Dozens of Palestinians were detained before dawn on Thursday in an Israeli military incursion in northern Gaza, witnesses said.
Israeli troops used loudspeakers to order residents of the Beit Hanoun area aged 16 to 60 to gather in a square, and then took away about 60 of them, according to Mohammed al-Kafarneh, who said he witnessed the incident.
The Palestinian Ramattan news agency said one of its cameramen, Ashraf al-Kafarneh, was among those taken.
An Israeli military spokesman confirmed the raid.
"During a routine activity by the Israeli army in the north of the Gaza Strip, about 60 wanted Palestinians were taken by security services to be interrogated," the spokesman told the AFP news agency.
Witnesses said armoured military bulldozers destroyed farmland during the incursion.
In a related development, a 29-year-old Palestinian civilian died of his wounds on Thursday, one day after he was hit by Israeli gunfire in southern Gaza, the head of the Gaza emergency services said.