You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Republic_of_the_Congo

Context:
Economic reform efforts continued with the support of international organizations, notably the World Bank and the International Monetary Fund. The reform program came to a halt in June 1997 when civil war erupted. When Sassou Nguesso returned to power at the end of the war in October 1997, he publicly expressed interest in moving forward on economic reforms and privatization and in renewing cooperation with international financial institutions. However, economic progress was badly hurt by slumping oil prices and the resumption of armed conflict in December 1998, which worsened the republic's budget deficit.

Question:
What caused reform efforts to cease in 1997?

civil war