Mine owners ruled out chances of finding any survivors.
"There are 66 miners missing and still trapped underground in the pits," said state-run Tanzania Broadcasting Corporation (TBC) radio, quoting the owners.
"There is no hope of finding anybody alive because it is their third day underground," the radio said.
Mike Temi, one of the owners, confirmed that 66 people were missing as of Monday morning.
"My husband is still down there. There are also two brothers-in-law of mine. All I want is to find their bodies"
Rosa Manka, wife of one of the miners
Jakaya Kikwete, the Tanzanian president, due to travel to the disaster area, said he was "shocked" to hear of the accident and the growing death toll.
Officials gave diverging counts of the number of miners who escaped or were rescued from the pits, where thousands dig to find the precious purple-blue mineral named after the country.
State radio, quoting the mine owners, said 93 people close to the surface escaped the flooding. Other officials said 35 escaped.
Philip Marmo, state minister at the prime minister's office in charge of disaster response, said the government had approached the army for assistance with the rescue effort.
Mizengo Pinda, the prime minister, said $0.4m had been allocated and 80 additional rescuers hired to bolster the operation.
Relatives of those missing gathered at the mine but held out little hope of anyone being brought out alive.
"My husband is still down there. There are also two brothers-in-law of mine. All I want is to find their bodies," said Rosa Manka, a young woman, sobbing as two aunts supported her.
In June 2002, at least 39 tanzanite miners died after inhaling carbon monoxide produced from a dynamite explosion, one of the many fatal accidents linked to mining in Tanzania.
Rescuers and miners had very little equipment at their disposal in their attempt to reach those trapped underground.
Poor weather conditions further complicated efforts to rescue the men.
Tanzanite One, a South African company which is operating a neighbouring pit, offered equipment to pump out flood water and dig a path towards the miners.
Tanzanite, a purple-blue shimmering stone, has only been found in northern Tanzania.
Many workers in Mirerani only receive food rations from their employers and are paid only if they hit tanzanite.
Tanzania's mining sector has expanded rapidly over the past decade after it underwent a process of economic liberalisation in the mid-1980s.
The country is the Africa's third-largest gold producer after South Africa and Ghana and is also rich in diamonds, emeralds, rubies and sapphires.
The mining sector contributes less than three per cent of the nation's GDP, but the rate should reach 10 per cent by 2025, according to a development plan outlined by the government.