Party general secretary B K Hariprasad said they will approach the Election Commission tomorrow.
Asked whether the party suspected internal sabotage in the elections including by former chief minister B S Hooda, he replied in negative.
Hariprasad alleged that there was deliberate fraud in the election by switching the pen meant for marking the votes so as to make the Congress votes invalid.
On his part, Hooda said there has been a "big conspiracy" and the truth should come out.
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"A probe by the Election Commission should be sought. This truth will come out in 24 hours," he said in Chandigarh.
Hariprasad had yesterday said that prima facie he saw a conspiracy from the government's side and said the party will find out the truth. "We will fight it politically and legally," he had said.
The defeat of Anand came as a bolt from the blue for the Congress and its high command, which was confident that its strategy to trounce BJP-backed media baron and independent candidate Subhash Chandra would succeed.
Hooda was not initially in favour of Anand as he was backed by INLD, the rival party in Haryana.