The family of Sara Zelenak say they are "distraught" after she was identified as the second Australian to have died during the weekend terror attacks in London.

Ms Zelenak, 21, had been reported missing after she became separated from a friend while on London Bridge on Saturday night (UK time).

Julie Wallace with her daughter Sara Zelenak. ( Supplied: Facebook )

Parents Julie and Mark Wallace travelled to the UK and have now been notified of her death.

Ms Zelenak's aunt Tara Abela paid tribute to her niece, who she described as a beautiful and happy woman.

"We are all so distraught that we have lost our little Sara," she said.

"She is the most beautiful, funny, happy, positive young lady with so much to live for and it was taken away too early.

"You can lose faith in humanity at these dark times but myself and the family has been so grateful for those around us and complete strangers offering any help or assistance."

"Julie just wants to bring her home now."

Sorry, this video has expired Colleague pays tribute to Kirsty Boden

On Tuesday night, the family of South Australian woman, Kirsty Boden, confirmed her death after the London Bridge and Borough Market attack.

London's Metropolitan Police released a statement on behalf of 28-year-old Ms Boden's family, saying "Kirsty was loved and adored by her family, friends and boyfriend".

"She was the most outgoing, kind and generous person who loved to help people," the statement read.

"Helping people was what she loved to do in her job as a nurse and in her daily life."

"As she ran towards danger, in an effort to help people on the bridge, Kirsty sadly lost her life."

Seven people were killed during the terror incident, which saw several men ram pedestrians on London Bridge before they attacked others with knives at the Borough Market.

Two other Australians were stabbed in the neck in the attack: Candice Hedge of Brisbane and Andrew Morrison of Darwin.

Ms Hedge required surgery and Mr Morrison required stitches.

'Such a beautiful, fun soul'

Mark Wallace with his stepdaughter Sara Zelenak. ( Facebook: Mark Wallace )

Ms Zelenak, who grew up on Brisbane's bayside, was working in the UK as a nanny and tributes have begun pouring in for her online.

Her close friend Sam Hetherington wrote on Facebook: "I can't believe we don't get to grow old together. Just Thursday I messaged you and you told me everything will always work out".

Tributes for Sara Zelenak left outside Morton Bay College on Thursday. ( ABC News: Allyson Horn )

Another friend Sophie Clark added: "Such a beautiful, fun soul. RIP beautiful girl, you will be dearly missed!"

Her high school, Moreton Bay College, wrote on Facebook that its "hearts are broken" by Ms Zelenak's death.

"Sara was a positive, popular student who always had a smile on her face," the school wrote.

"She embodied the values of Moreton Bay College and was adored by her peers and staff. This is how she will be forever remembered."

An online fundraising campaign, originally set up to collect money to send Ms Zelenak's parents to the UK, has been re-opened in light of the confirmation of her death.

UK police make 13th arrest

Meanwhile, the Metropolitan Police said they were executing a search warrant on an East London property on Wednesday morning (UK time).

A 30-year-old man from Ilford was arrested on suspicion of commission, preparation or instigation of terrorist acts and is in custody.

The Met said 12 others arrested as part of the investigation had all been released without charge.

Three terrorists who carried out the attacks were shot dead at the scene.