NEW : 52 others injured , police say . NEW : Police are investigating the incident as a hate crime. The explosion happened around 4 p.m. at Emab Plaza in Abuja 's Wuse II business district .
NEW : 52 others injured , police say . NEW : Authorities step up security , surveillance around Abuja after blast . The explosion happened around 4 p.m. at Emab Plaza in Abuja 's Wuse II business district .