ABUJA (Reuters) - Nigeria’s upper house of parliament will investigate a railway concession the government wants to grant to U.S. firm General Electric over possible violations by Nigerian officials, lawmakers said on Tuesday.

The lower house had already launched a similar inquiry last month into talks between the government and GE on a railway concession deal worth around $2 billion.

Nigeria has been looking for partners to overhaul its ageing railway system, which was built mainly by British colonial rulers before independence in 1960.

The Senate wants to investigate whether the government had violated rules by opening talks with the U.S. firm without consulting parliament or other state bodies, lawmakers said.

“The Ministry of Transport has violated the provisions of the Public Enterprises Act, 1999 by unilaterally engaging the General Electric for the concessioning the of the Western (Lagos-Kano) and Eastern (Port Harcourt-Maiduguri) rail lines,” a motion approved by Senators said.

It refers to two north-south rail lines the government wants GE to rebuild. The lawmakers did not make any allegations of wrongdoing against the firm.

The government said last month more talks were needed with GE on the possible concession.

Nigeria, suffering from a slump in crude exports, wants to boost exports of non-oil products but lacks roads or functioning railways.

It has already signed two deals worth around $5 billion with China Civil Engineering Construction Corp (CCECC), part of China’s state-owned railway construction firm, to modernize several railway lines, the Nigerian Transport Ministry has said.