The riots started after rumours that Rwandans were behind recent ritual killings in the city.
More than 250 people have been arrested after more than 60 Rwandan-owned shops were looted in two days of violence.
Six people have been murdered since March and their body parts removed.
Rumours circulated that the body parts would be used as charms to ensure success in business.
“No baby or human body parts were found in any fridge belonging to any foreign national. These statements are coming from people with criminal minds to create alarm among the members of the public and justify their criminality,” police spokeswoman Charity Munganga said in a statement.
She warned that it was an offence to spread “false rumours” that caused alarm and the police would not hesitate to arrest those doing so “regardless of the medium they are using”.
“We are appealing to the members of the public not to believe any statement they see on social media which is not confirmed by the police.”
Rwandans are the largest group of immigrants in Zambia, owning shops in the densely populated areas which have been affected by the riots.
They number about 6,000, and many of them came to Zambia as refugees fleeing the 1994 genocide in their home country.
The BBC’s Meluse Kapatamoyo in Lusaka says the riots began in two poor neighbourhoods on Monday and spread to other areas on Tuesday.
Young men ransacked shops, possibly reflecting growing frustration at the high levels of unemployment and the rising cost of living, our correspondent says.
Riot police had to be deployed and many Rwandans fled to police stations to take shelter.
Ms Munganga said police officers were still deployed to all areas – no rioting has been reported on Wednesday.
The violence shocked many Zambians who say they cannot recall such hostility towards foreigners, our reporter says.
Ritual killings are also rare in in the southern African nation, she says.
The home affairs minister said on Tuesday, after visiting areas hit by the riots, that 11 people had been detained on suspicion of being involved in ritual killings.
Source: BBC News