The NIMASA DG said some of the crimes in the state were carried out by illegal immigrants whose identities were unknown to the government.
The returnees arrived in Kano in three luxury buses organised by the International Organisation on Migration.
The building, said to have been under construction, had collapsed during torrential rainfall.
The nine dead bodies were recovered from a collapsed building affected by the explosion and deposited at the mortuary.
“Two additional bodies including a four-year-old boy and a female youth corps member recovered, making 10 deaths.”
An old three-Storey building collapsed at No 24 Ibadan Street, off Herbert Macaulay Way, Ebute-Meta, on Sunday night at about 10:56 p.m.
The recovered bodies were those of a mother and her child, while the rescued persons included seven children and 16 adults.
“Those who should tell the story and give insight into the incident are all dead…We will soon come out with a report on the incident.”
NEMA South-West Zonal Coordinator, Ibrahim Farinloye, made the announcement on Wednesday in Lagos.
The crisis which occurred on March 7, was said to have been as a result of a land dispute between two communities.
