He said the National Investigation Agency, which is probing the case, has got some clues and there is progress. He, however, refused to divulge details.
"Some people have been arrested and they are being interrogated," Singh told reporters when asked about the progress of the case.
"We have clues. There is progress also. But we do not want to disclose whatever progress we have made as it will hamper the investigation," he said on sidelines of a function here.
The NIA had on Tuesday raised the reward money from Rs 5 lakh to Rs 10 lakh for anybody giving information about the perpetrators of the blast.
