A total of 242 serving and retired officers' accounts of the events surrounding the deaths of 96 Liverpool fans nearly 25 years ago are suspected of having been amended, the Independent Police Complaints Commission (IPCC) said.
As of January 21, 160 officers whose accounts are suspected of having been amended had been interviewed, the IPCC added.
Britain's worst sporting disaster happened at Hillsborough Stadium, Sheffield, on April 15, 1989 during Liverpool's FA Cup semi-final against Nottingham Forest. Thousands of fans were crushed on the terrace.
IPCC deputy chairwoman Rachel Cerfontyne said: "We are nearing completion of the interviews of those officers whose accounts were subject to amendments.
"This means we are beginning to focus on those key people who are of significant interest to us and we expect to interview those before the start of the inquests.
"That will be a significant step as we expect to be identifying and interviewing people as suspects."
The police watchdog also revealed Metropolitan Police commissioner Sir Bernard Hogan-Howe is subject to a second, separate investigation in relation to public statements made over whether he gave an account to the Taylor Inquiry, which was held after the tragedy.