The head of the Toronto police G20 investigative team described four of his at-large suspects as being among the "worst of the worst" with respects to the vandalism committed on June 26.

"They are single-handedly responsible for thousands and thousands of dollars worth of damage to the city infrastructure and the downtown core," Det. Sgt. Gary Giroux told a Thursday news conference.

He drew attention to one suspect, with a covered face, seen attacking business windows with a small pick hammer.

Giroux thinks the majority of the individuals in Thursday's photo release are not from the Toronto area.

"I know personally that two of them are Americans" from the New York City area, Giroux said, adding they have a detective embedded with the New York police -- and vice versa.

There is also a detective working with border security agencies to track down suspects who may have crossed the border to engage in the mayhem of June 26, the first day of the G20 summit of world leaders at the Metro Toronto Convention Centre, he said.

"Once these criminal cases have been established, extradition from the United States will be sought by the G20 task force," Giroux said.

"These individuals came to our city for the sole purpose of doing damage and ended up (being) some of the most offensive individuals for violence and damage in the city that night," he alleged.

The photos and video have been sent to the Montreal police's intelligence bureau and will be shared with news outlets in that city, he said.

Giroux said they have sequences of photos and video of suspects before, during and after the destruction. The images came from undercover police in the crowd as well as members of the public, he said.

Arrests to date

To date, police say they have made 20 arrests and laid 60 Criminal Code charges. One youth is among those charged.

Giroux said he believes his team has rounded up most of the suspects from the GTA and southern Ontario.

Most of those arrested to date are accused of committing vandalism-related crimes in the Queen Street West and Spadina Avenue area, he said.

"Generally, they were GTA residents and unmasked and therefore identifiable, and they were the subject of the first 20 (photos)," he said.

The June 26 violence occurred when a group of vandals using so-called Black Bloc tactics emerged from a large, peaceful, labour-sponsored anti-G20 march and went on a destruction spree in the downtown core outside the G20 security zones.

Police announced one new arrest in connection with that mayhem. They arrested Brandon Martin Witzke, 21, of Toronto on Wednesday and charged him with mischief over $5,000.

Police also said they have re-arrested Kurt Roarco, 22, of no fixed address on a surety warrant.

Roarco had previously been charged with:

mischief over $5,000

arson - damage to property

failure to comply with a probation order

No allegations against Witzke or Roarco have been proven in a court of law.

Giroux said his team continues to monitor those who had been previously charged and will re-arrest them if they violate bail conditions.

Police have never put a total damage value on the destruction that occurred on June 26. They have said six police cars were attacked, with four being torched. Five of those cars were a total loss, and their replacement value is estimated to be $65,000 to $70,000.

Giroux said his team's focus has been on the destruction that took place on June 26.

More than 1,100 people were arrested in connection with G20 protests, but the majority were never criminally charged. On Monday, 58 of 304 saw their charged stayed or withdrawn by the Crown.

About 231 cases remain before the courts, including those of 17 people the Crown alleges are ringleaders.

Giroux said he is confident he has the evidence to obtain convictions in the cases of the so-called worst of the worst.