VANCOUVER - The Vancouver Sun Run will donate $10 from every late entry for Sunday's race to help victims of the bombings at the Boston Marathon.

Online registration closed at midnight on Tuesday for Canada's largest 10-kilometre run, but organizers say people who want to participate can still sign up in person at BC Place beginning at 4 p.m. Thursday.

The fee for those who register late goes up by $10 to $60, but the plan is to donate that $10 from every late entry to the Boston bombing victims, said Jamie Pitblado, vice-president of promotions for The Vancouver Sun and The Province.

He said the money would go to One Fund Boston, an official charity that's collecting donations for the victims and their families.

If a surge in registration continues, Sun Run organizers could raise anywhere from $25,000 to $40,000.

Registration for The Sun Run spiked again on Tuesday after doubling on Monday from the previous year. Pitblado said 965 new participants signed up on Tuesday, compared with just over 500 on the same day last year. On Monday, 691 registered, compared with 343 the year previous.

As online registration closed at midnight, there were 46,048 participants.

"It was unbelievable," said Pitblado on Wednesday. "The trend continues, the swelling of support for those in Boston."

Runners will start the race Sunday morning with an official tribute to Boston, although Pitblado said organizers are still working out the details.

Yellow and blue are expected to colour the streets, as many participants don Boston's official hues to show support for the bombing victims.

Premier Christy Clark, who will run as part of a team on Sunday, plans to wear yellow and blue to honour the victims, said spokesman Sam Oliphant.

Explosive devices made from pressure cookers stuffed with nails and ball bearings killed three people and injured more than 160 people as runners were crossing the finish line Monday at the Boston Marathon.

The person or group responsible for the attack remained unknown Wednesday, as investigators faced the daunting task of combing through thousands of videos and photographs.

Also Wednesday, more Vancouverites returned home from Boston with horrific tales of narrow escape and aftershock, while others, such as Stan and Sally Wong, remained in the U.S., recovering from the ordeal.

The couple, speaking from Washington D.C. on Wednesday — amid heightened security after a suspicious letter laced with poison was sent to President Barack Obama — said they were still in shock.

Sally was running at the exact location where the first bomb exploded and said if she had been running on the other side of the road, she might have been badly injured or killed.

"Something just came exploding out of my left side, and I thought it was a restaurant explosion," she said.

When she heard the second explosion coming from where her husband Stan had been waiting on the sidelines, and had moments earlier high-fived her as she ran past, she began to panic. So she sprinted across the finish line and was one of the last runners they let through before they stopped everyone.