In the six weeks since 1,000 young people torched a TV news van and pelted police officers with bottles near Fanshawe College on March 17, London police have charged 42 people with 103 offences.

Of the latest group of four, announced by the police April 27, three are charged with taking part in a riot.

None of the accused already named face that particular charge.

Police would only say that the latest trio's level of involvement in the fracas warranted stronger charges than unlawful assembly.

"In relation to the suspects charged with taking (part) in a riot, we don't anticipate charging any of the earlier suspects with these new charges," Const. D'Arcy Bruce said Monday.

"Taking (part) in a riot is an indictable offence. As such, anyone convicted is liable to imprisonment for a term not exceeding two years."

Bruce said it's extremely unlikely anyone would receive such a harsh sentence.

A spokesman for Vancouver police said numerous people have been charged with taking part in the Stanley Cup riot, but declined to say what in particular triggers the charge.

More than 100 people have been arrested in the 2011 riot after the Vancouver Canucks lost Game 7 of the final.

University of Toronto law Prof. Hamish Stewart said he couldn't explain why only three people have been charged with taking part in the Fleming Dr. riot when hundreds were there, but he did say the distinction between riot and unlawful assembly is clear.

"Section 64 (of the Criminal Code) defines a riot as 'an unlawful assembly that has begun to disturb the peace tumultuously.' So a riot might be understood as an aggravated version of unlawful assembly."

In other words, simply being there is being part of an unlawful assembly, while participating -- or fanning the flames, so to speak -- might land someone the more serious charge.