Nigeria’s election commission has declared the gubernatorial poll in Imo state inconclusive due to the large amount of canceled votes compared with the margin of win by the All Progressives Congress (APC) governorship candidate, the Premium Times reports. The APC opposition party has so far won 19 of the 29 governor seats up for grabs in Saturday’s elections.

A collation of results in Imo state showed the APC governorship candidate, Rochas Okorocha, won 79,529 more votes on Saturday than the Peoples Democratic Party (PDP) candidate, Emeka Ihedioha. But that margin was significantly less than the 144,715 votes canceled on Monday by Nigeria’s Independent National Electoral Commission due to irregularities in some areas of the southeast state. The INEC said Sunday violence targeting polling stations had marred the election in Imo, among other states. The date for a supplementary election in the canceled zones will soon be announced, the Premium Times reported.

This is the second time the INEC has declared the gubernatorial election in Imo state inconclusive. The election commission fixed a supplementary election May 2011, less than two weeks after the governorship poll was not held in certain wards and local government areas. Okorocha was leading the race with a slim margin against then-Governor Ikedi Ohakim. Okorocha, who at the time was the candidate for the All Progressives Grand Alliance opposition party, went on to win the supplementary election.

The All Progressives Grand Alliance was one of four opposition parties that merged in 2013 to form the APC, with the goal of capsizing the PDP’s plurality rule. If Okorocha is re-elected governor of Imo state, the APC will succeed in retaining the only state it controls in Nigeria’s petroleum-rich southeast region. The PDP won back a key governor seat in Nigeria’s oil hub of Rivers state, after losing the presidency and its national legislative majority, Reuters reports.