Maisy Weicherding, Uzbekistan researcher of the human-rights watchdog, told Aljazeera.net on Tuesday: "There have been reports of house to house searches by the government trying to detain anyone with connections to organisers of the demonstration or to the jail break.
"What we need to find out is how many have been detained and if those detained have access to lawyers and whether they have been tortured."
London-based Amnesty International (AI) called on Uzbekistan to allow an independent investigation into the events.
In a statement released on Monday, AI condemned the reported use of excessive force against civilians in Andijan, and called on the authorities of Uzbekistan to allow a prompt and independent investigation into the events with the results made public and those responsible brought to justice.
The Uzbekistan government has yet to react to AI's allegation.
AI said it was concerned Uzbek authorities would use the events in Andijan to justify a further clampdown on dissent and freedom of expression in Uzbekistan, and that this would lead to waves of arbitrary arrests nationwide in the name of "national security" and the "war against terror".
Reports say soldiers shot at
innocent civilians in Andijan
Weicherding said she hoped the investigation would involve international experts.
She said that one of the main purposes of the investigation would be to establish the identity of those killed.
AI told Aljazeera.net that at least 12 people were buried without identification as no relatives came forward to claim them. Names of the dead must be established.
Reports of soldiers roaming the streets and shooting innocent civilians filtered out of the country even though the government imposed a ban on foreign media.
Opposition groups put the figure at 745 people killed by government troops.
The crackdown in Andijan came on Friday after protesters stormed a prison, freed inmates and then seized local government offices. But many of the demonstrators were citizens complaining about poverty and unemployment.
Britain and the United Nations also urged Tashkent on Tuesday to show restraint and allow humanitarian groups access to the area.
A spokeswoman for UNDP's Tashkent office told Aljazeera.net they still had not been given free access in the Fergana valley and the situation there remains unclear.
"We have not found masses of people wishing to leave the region. At this stage people need to be reassured about their future"
ICRC regional delegation head
However, the International Committee for the Red Cross (ICRC) has said they have had "good access" in the Fergana valley.
Rolin Wavre, head of the ICRC regional delegation, told Aljazeera.net: "We have had a team in the Fergana valley since mid-day on Saturday and we have had good access in the region."
The ICRC said patients in hospitals were being well treated.
Wavre also said that across the border in Krygystan's Jalalabad, more than 500 refugees were being well treated with all their basic needs - food, water and medical aid - being met.
"We have not found masses of people wishing to leave the region. At this stage people need to be reassured about their future," Wavre said.