Philadelphia police and FBI officials continued yesterday to turn up the heat on Floyd, the only suspect still being sought in the weekend slaying of Sgt. Stephen Liczbinski, the married father of three.

City officials have announced that a reward of more than $140,000 is being offered for information leading to Floyd's capture. And Floyd's mug shot is being displayed on seven Clear Channel digital billboards across the city.

Homicide detectives spoke with some of Floyd's relatives, hoping they could bring the chase to a close. "They realize the gravity of the situation," one investigator said.

Cops continued to check out tips, including one that seemed promising from the daughter of a Philadelphia police officer.

She thought she had seen a man who matched Floyd's description wearing a wig on a New Jersey Transit train, in Hamilton yesterday morning.

An intense search was launched after the man fled the train near Newark, N.J., where, a police source said, Floyd is known to have relatives.

But by last night, investigators were still searching for the man, who left his wig on the train.

Earlier in the day, at a City Hall news conference, Mayor Nutter implored Floyd to surrender and warned those close to him against helping him.

"It is time to put this to an end, face up to what you have done," said Nutter, flanked by top police brass, District Attorney Lynne Abraham, Deputy Mayor for Public Safety Everett Gillison and FOP President John McNesby.

Nutter also asked that anyone with information about Floyd's whereabouts contact an FOP tip line, and stressed that there would be consequences for those who don't.

"If you withhold information . . . you will be prosecuted to the fullest extent of the law," Nutter said.

He asked city residents to pray for Liczbinski's family, noting that he spent time at their home on Sunday night.

"This is tremendously difficult," he said.

Of Liczbinski's widow, Nutter said, "Michelle is exhibiting tremendous strength under an enormous amount of pressure."

Homicide investigators continued to try to guess Floyd's next move.

One detective noted that Floyd has no money to pay for a trip out of town.

The $40,000 that Floyd, 33, and his alleged accomplices, Levon Warner, 38 and Howard Cain, 33, robbed from a Bank of America inside a Port Richmond ShopRite on Saturday has been recovered. Warner is in jail and Cain was shot to death.

A police source said investigators believe that it's unlikely that Floyd will try to flee south, as John "Jordan" Lewis did after he allegedly killed Officer Chuck Cassidy last fall.

"We're focusing in this area up here right now," the source said.

Investigators are also looking into the possibility that Floyd, Cain and Warner could have been involved in other robberies in the area. Floyd and Cain wore Muslim garb during Saturday's robbery and Warner wore a mask and a dreadlock wig, police said.

The source said that investigators are looking at a Southwest Philadelphia robbery from last week, when at least two men dressed as Muslim women pistol-whipped the office manager.

Police believe that the men met at Mahanoy State Correctional Institution, and might have been involved in some sort of prison uprising - although it was unclear last night when that occurred.

Floyd entered the state prison system in 1995, when he started a one-to-five-year sentence for robbery. Floyd had been convicted of robbing a 15-year-old - with the help of his cousin - in 1994.

State Department of Corrections spokeswoman Kelli Kishbaugh said that Floyd completed his sentence in 1999, but was back behind bars in May 2002, again for robbery.

Floyd escaped from a halfway house in Reading on Feb. 27, Kishbaugh said.

Cain, whose arrest history dates from 1993, entered prison in 1997 on a sentence of nine to 18 years for robbery and conspiracy, according to court records.

Leo Dunn, a spokesman for the state Board of Probation and Parole, said Cain was paroled in August 2006.

Warner, a once-promising heavyweight boxer, had bounced in and out of state prisons beginning in 1991, when he was locked up on robbery charges, Kishbaugh said. He was paroled in 2004.

Tipsters can contact police at 215-686-TIPS. *

Staff writer Catherine Lucey contributed to this report.