Security 'a facade'
Police were focusing their search on the country's air and sea ports, a security official said, adding that museum staff will be interrogated and that state prosecutors have launched two separate investigations.
The official said security cameras and alarms at the museum had long been out of order.
"The cameras had not been working for a long time, and neither had the alarm system," he said.
"The museum officials said they were looking for spare parts [for the security system] but hadn't managed to find them" by the time the theft took place, he added.
Al Jazeera's Ayman Mohyeldin reported from Cairo, said the theft raised real concerns over the security of precious artwork on display throughout the country.
"[It's] raised serious questions about the conditions of many of Egypt's top museums that house some of the world's most notable pieces of art as well as ancient antiquities," our correspondent said.
Farouq Hosni, Egypt's culture minister, announced on Saturday evening that two Italians had been arrested at Cairo airport trying to smuggle the painting out of the country.
But he later backtracked on the claim, publicly admitting that the authorities were still working to retrieve the picture and blaming a subordinate for giving "inaccurate" information.
The official who had said the painting was in the possession of police at Cairo airport, switched off his mobile phone on Saturday evening and could not be reached for comment.
Another official described the incident as "embarrassing and chaotic".
This is the second time the painting by the Dutch-born post-impressionist has been stolen from the Cairo museum.
Thieves made off with the canvas in 1978, before authorities recovered it two years later at an undisclosed location in Kuwait.
One year later, a duplicate was sold for $43 million in London, sparking a debate in Egypt whether the returned painting was, in fact, a fake.
Authorities have never fully revealed the details of the first theft of the painting.