Nigeria’s military has warned of a plot by the Boko Haram militant group to poison water sources in northeast Nigeria, various media outlets reported over the weekend. Officials have urged citizens to stock up on water and other necessary commodities while they investigate the issue.

"The Command wishes to inform the general public that Boko Haram terrorists plan to buy large quantity of rat poison and other poisonous items from markets in Nigeria to enable them poison water sources particularly in the North Eastern states," the army said in a statement.

The warning comes one day after Nigeria’s secret police arrested and charged some 45 suspected members of Boko Haram who were reportedly plotting to attack the country’s financial hub, Lagos.

Boko Haram has waged a brutal insurgency in Nigeria’s northeast region in hopes of driving out the Abuja-based government and setting up an Islamic state in its place. The restive region has seen more than 15,000 deaths and more than a million people displaced since the start of the insurgency in 2009.

President Muhammadu Buhari, who came to power in May promising to end Boko Haram violence, has given his top military commanders until the end of the year to defeat the insurgents. After coming to power, he restructured the military and replaced the heads of the army, navy and air force in an attempt to refocus military efforts on defeating Boko Haram.

Since then, Boko Haram has experienced significant losses, but has stepped up their attacks on civilians. More than 1,400 Nigerian civilians have been killed since Buhari came to power. Boko Haram released a video pledging allegiance to the Islamic State group based in Iraq and Syria in March.

Four suicide bombers were reportedly killed in a failed attack Sunday in Maiduguri, a northeast Nigerian city that has been at the heart of much of the violence in recent years.