The National Accountability Bureau, Pakistan's main anti-corruption agency, is pursuing the case involving "rental power plants" and no file has been closed.
The NAB could summon anyone, including the premier, if he or she is required in the investigation, The News daily quoted an official as saying.
"Yes, the probe is still on and the Prime Minister could be summoned. But that would depend on the gravity of the situation as the investigation team will decide whether the Prime Minister should be summoned in person or whether a questionnaire should be sent to him," NAB spokesman Zafar Iqbal Khan said.
The investigation team will decide whether the presence of a particular person is required or if a questionnaire could serve the purpose, he said.
In the past, NAB had sent a questionnaire to former premier Yousuf Raza Gilani on the issue of the appointment of the head of a state-run firm.
Similarly, NAB could send a questionnaire to Prime Minister Ashraf in the power projects case, Khan said.
Asked about the general perception that NAB has closed the file against Ashraf, the NAB spokesman said the probe was still ongoing.
The NAB twice interviewed Ashraf before he became the premier last week. On March 30, the Supreme Court declared all contracts signed by the government for rental power plants as illegal and directed authorities to take legal action against those responsible for clearing the projects, including Ashraf.
The apex court directed NAB to probe all ministers and government functionaries who played a role in clearing the power projects since 2006 and to submit fortnightly progress reports.
Ashraf took over as premier last week after the apex court disqualified Gilani.
He was Power Minister when contracts were signed for several rental power projects, which were part of the Pakistan People's Party-led government's strategy to overcome a crippling energy shortage.
A two-judge bench headed by Chief Justice Iftikhar Chaudhry said in its order that the power projects were a "total failure" as they produced only 120 MW of electricity.
The bench said the government had committed illegalities by paying a 14 per cent advance payment of billions of rupees to bidders.