Hangzhou authorities have released more details in the case of a nanny accused of setting fire to an apartment in Hangzhou, Zhejiang province, China News Service reported on Monday.

At a news conference, the authorities said the nanny had used her mobile phone to learn how to set a fire. They also said the property management company failed to maintain safe facilities and to provide emergency response.

The police said Mo Huanjing, 34, confessed after her arrest, and was charged on July 1 with arson and theft in connection with the blaze that swept through an apartment in a residential building on June 22. The fire killed a mother and her three children, aged 6 to 11 years, Li Bing, deputy director of the Shangcheng district public security bureau, said at the news conference.

Mo was addicted to online gambling, Li said. She had worked as a babysitter since 2015 in Shaoxing, Zhejiang province, and in Shanghai, but was fired three times after being accused of theft.

She had worked for the family caught in the fire since September and had stolen items she subsequently pawned for 130,000 yuan ($19,000) to pay off gambling debts. Mo also borrowed 114,000 yuan from her employer, claiming she needed to buy a house for her parents.

During the investigation, the police discovered that Mo had searched such key words as "lighter", "sofa fire" and "curtain fire" from 2 am to 4 am on the day of the blaze, the news service reported.

Later, at 4:55 am, Mo used a lighter to set fire to a book on a tea table. The fire spread to the sofa, got out of control and frightened Mo, who fled, leaving the mother and three children to die.

Firefighters arrived at the scene at 5:11 am, but the fire engine was blocked. Firemen rescued seven people but failed to reach the blazing room.

Insufficient fire hydrant pressure prevented fire suppression and delayed the rescue effort, the report said.

According to Chen, the property management company had many problems with its emergency preparedness, including staff members who didn't know how to switch on a fire hydrant pump manually.