Investec has kept its 'hold' rating for BP but has hailed a 'very strong' first-quarter result from the oil giant on Tuesday morning.Clean net income came in at $4.22bn for the first three months of the year, a "substantial" 29% above company-compiled consensus, the broker said. Lower seasonal costs and a strong trading performance helped both the Upstream and Downstream divisions beat forecasts.First-quarter clean earnings per share (EPS) were 0.22 cents, achieved at an Brent oil price of $122 a barrel. Analyst Neill Morton said: "When annualised, this implies [EPS of] $0.88 for the full year. This is +10% versus Bloomberg consensus. We are at $0.78 (at $105/bl)."He said that current 2013 forecasts are expected to rise modestly. Investec has placed its target price under review.The stock trading in line with the sector average - trading at 9.1 times earnings - with an average dividend yield (5.2%), Morton said."The statement refers to higher costs, lower production and a weaker downstream in Q2 so earnings upgrades may be more muted than the Q1 headline figures might suggest. Nevertheless, this is an encouraging start to the year for BP."The stock was up 3.62%at 473.3p by 10:12.BC