Both denied earlier reports that a bomb had exploded in Fida, a working-class neighbourhood of Casablanca.
Three suspected suicide bombers blew themselves up on Tuesday following a raid in which a fourth suspect was shot dead, police sources said.
"There was no explosion," said the government official. "Police made an arrest. It was a fifth member of the cell who was still hiding in the area."
The cell was part of a bigger group that police have been looking for since March 11, when the suspected leader of a suicide squad detonated his explosives belt in an internet cafe to escape arrest, police sources said.
Police found the fifth man during a routine search and arrested him after he threatened to blow himself up, state news agency MAP cited police sources as saying.
It turned out the man was not carrying any explosives and had apparently entered the house to ask for food, MAP added.
"There was no explosion. The police seem to have arrested the last of the terrorists whose house they raided on Tuesday," a local resident said by telephone. "It was about 1km from their safe house."
Chakib Benmoussa, the Moroccan interior minister said late on Wednesday he suspected three to four members of the group might still be on the run.
An increase in extremist activity across the Maghreb in recent months has raised fears of a coordinated campaign by armed groups wanting to establish Islamic rule in the region.
On Wednesday, the Algeria-based al-Qaeda in the Islamic Maghreb claimed responsibility for bombs in the capital Algiers that killed at least 30 people.