The NACC said its panel looking into the matter had not obtained sufficient evidence to decide on Ms Yingluck's fate, though the investigation had made progress.
Revealing this confidential information would make it even harder for the NACC to investigate further, NACC deputy secretary-general Witthaya Arkompitak said.
Meanwhile, more rice farmers affected by the rice-pledging scheme have started blocking roads in their provinces demanding payment for their rice pledged under the scheme, which has been overdue for months.
In Phitsanulok, more than 500 protesters gathered at the Indo-China intersection blocking the road and demanded they be paid about 6 billion baht of overdue payments before Jan 31, or else they will step up their protest.
If the government fails to make the rice-pledging payments in time, the farmers will consider joining the People's Democratic Reform Committee (PDRC) in Bangkok, they said.
The Phitsanulok farmers also demanded the government cover the interest on the loans they had sought using their rice-pledging certificates as collateral. They said they had applied for the loans because they needed money to survive while they waited for their payments from the government.
They will continue to block the roads until they get a satisfactory answer from the government.
In Kamphaeng Phet, more than 200 rice farmers have started to block the Nakhon Sawan-Kamphaeng Phet road with their tractors and motorcycles in a similar protest.
Cars travelling between the North and the Central region through Kamphaeng Phet had to use a bypass to avoid the blocked road.
Surachet Siniang, chairman of the rice farmers' club of the province, said about 40,000 farmers are waiting for their payments which come to about 10 billion baht in total, and they have yet to receive a clear answer from the government about when they will get paid.
In Ratchaburi, more than 500 rice farmers have decided to block the Wang Manao intersection that serves as a gateway to the southern region.
The road-block protest in Ratchaburi is expected to take place on Friday, said Wichit Phanphian, president of Ratchaburi's rice farmer council.
About 300 farmers from Sing Buri, Lop Buri, Suphan Buri and Ang Thong have started to block the Asian Highway, both inbound and outbound lanes, in Sing Buri.
This protest has resulted in serious traffic congestion.
Meanwhile, Prapat Panyachartraksa, chairman of the National Farmers Council, said farmers could be paid for their pledged rice within three weeks.
"Caretaker Commerce Minister Niwatthamrong Bunsongphaisan assured me on the phone on Monday that farmers would be paid for their pledged rice within three weeks," he told reporters at a seminar on political deadlock held at Kasetsart University on Thursday.