Toronto police divers searched the waters off Woodbine Beach in the city’s east end Monday as part of their investigation into the disappearance of a PhD student who went missing four days ago.

Zabia Afzal, 30, was last seen Thursday morning near Toronto’s Ashbridges Bay park, along the shores of Lake Ontario.

She had used a ride sharing app to travel from Vaughan to Woodbine Beach around 10 a.m. that day. Police have since recovered her shoes and cellphone near the beach.

Her brother Zubair Afzal told CTV Toronto that his sister has suffered from depression.

“She has depression. Definitely this is not something we can ignore. This is out of her character to do something like this,” he said.

But Afzal always keeps in touch with her family, he noted. “She is in constant communication. She is very vocal, when she has something on her mind, to let us know.”

On Sunday, Zubair Afzal helped organize a search that saw more than 40 volunteers place roughly 7,000 posters across the city, including the Toronto Islands.

Afzal, a Vaughan resident and a public health PhD student and instructor at York University, is described as a strong advocate for women’s rights active in the Thorncliffe Park area of central-east Toronto.

“She’s the most brilliant person I know,” one of Afzal’s classmates told CP24. “She uses her brilliance for the good of the society that we live in. She is deeply moved by injustices big and small.”

York University has also been spreading the message to the university community to pass on any information they might have about Afzal’s disappearance.

“We have been sharing updates with York community members and encouraging anyone who has information to connect directly with the police or our community safety team immediately,” York spokesperson Barbara Joy said in a statement.

Afzal is described as five-foot-four with shoulder-length, dark-brown hair. She was last seen wearing black pants, a black hoodie and a green floral shirt.

Anyone with information on Afzal’s whereabouts is asked to contact York Regional Police or Crime Stoppers.

Another search party gathered near the East York Town Centre Monday night to canvass and put up more posters in hopes of learning anything about the woman’s whereabouts.

“Definitely it is not something that we are able to cope with. It is a difficult situation,” said her brother. “Obviously we are trying to stay strong, and very optimistic and hopefully at this moment."

With a report from CTV Toronto’s John Musselman