ABUJA - Nigeria’s anti-corruption agency is investigating the speaker of the lower chamber of parliament, according to a document seen by Reuters, part of a campaign against graft being waged by President Muhammadu Buhari’s government. Yakubu Dogara, the speaker of the House of Representatives, is under investigation by the Economic and Financial Crimes Commission over allegations he illegally added figures to Nigeria’s 2016 budget after it was passed by parliament, according to a letter from the watchdog dated June 9 and seen by Reuters. A spokesman for Dogara did not respond to repeated calls for comment.