Jodie Chesney's family support tougher knife laws
The family of a 17-year-old girl killed in east London have backed a call for longer jail terms for people carrying knives.
Jodie Chesney died after being stabbed in the back in a park in Romford.
Relative Karen Chesney wants people to be jailed for 25 years for using knives, and 10 years for carrying them.
Metropolitan Police Commissioner Cressida Dick said officers were doing "everything in their power" to catch Jodie's killer.
An online petition calling for harsher punishments has been signed more than 33,000 times.
Ms Chesney shared the petition on Facebook and urged people to "please sign" it.
The current maximum penalty for an adult carrying a knife is four years in jail and an unlimited fine, with prison sentences only handed to repeat offenders.
Jodie was killed as she played music with friends in the park in Harold Hill on Friday.
Her grandmother Debbie Chesney said the family were in "shock" after a "nightmare" few days.
In a previous social media appeal, she said: "We don't want anyone else to go through what our family is suffering right now.
"This has to stop, there are too many young people having their lives cut short by needless violence."
Ms Dick said police "need help" in the search for two suspects involved in the killing.
"We've already had lots of calls from the public but anybody who was in that area... on Friday evening, please get in touch, give us information," she said.
"Somebody out there knows who committed this crime."
The deaths of Jodie and 17-year-old Yousef Makki, who was killed near Altrincham on Saturday, have sparked a national debate about ways to tackle knife crime.
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Prime Minister Theresa May said there was "no direct correlation" between falling police numbers and a rise in violent crime.
However, Ms Dick disagreed, saying there was "some link".
Mrs May has asked the Home Office to co-ordinate a series of urgent meetings and engagements on knife crime.
Her spokesman said the prime minister had told cabinet Jodie and Yousef's murders were "absolutely appalling crimes".